The assembly of a brain probe assembly employed in brain research is quite challenging from both a structural and an electrical standpoint.
Structurally, probes must not fray or in any way come apart when pushed through the dura, a tough membrane covering the brain, and other brain tissue. Probe should have enough strength and rigidity to broach the dura without the need for assistance by, for example, a guide tube or an initial incision.
Moreover, probes must not break, running the risk of leaving a fragment in the brain. Also, they must not cause undue damage to tissue at the sensing site. Inevitably, the tissue separating the sensing site from the brain exterior will suffer some damage as a probe is pushed to its destination.
Electrically, one should note that field signals to be detected in the brain, are typically of the order of 100 to 500 xcexcvolts. The low amplitude of these signals makes it necessary to amplify them as physically close as possible to their source. In fact, the signals involved are so minute that variations in circuit geometry could well affect significantly the detection processing of the signals. It is also highly desirable to minimize cross-talk between any two signals. Given the tight geometries allowable for brain probe design, these requirements are difficult to meet simultaneously.
In a first separate aspect the present invention is a bio-probe having a base and a tip, and comprising a core of substantially rigid, high-strength material. The core tapers inwardly from the base to the tip and a set of conductors extend longitudinally about the core. In addition, dielectric material, substantially electrically isolates each conductor from its surroundings. Also, a set of apertures are defined by the dielectric material to the set of conductors, thereby defining a set of electrodes.
In a second separate aspect, the present invention is a method of producing a bio-probe. This method includes the step of providing a tapering core of substantially rigid material. The core is then coated with dielectric material and this dielectric material is coated with a first layer of conductive material. The conductive material is then divided into longitudinal traces, extending from the base into proximity to said tip. The conductive material is then coated with a second layer of dielectric material. Finally, portions of the second layer of dielectric material are removed to form apertures to the conductive material, thereby forming electrodes.
In a third separate aspect, the present invention is a bio-probe assembly for measuring bio-electrical signals, comprising, a probe portion having a distal end and a proximal end and a set of electrodes at said distal end for detecting the bio-electrical signals. Each electrode is connected to a longitudinal conductor, extending to the proximal end and a set of substantially identical amplifier circuit cards connected to the longitudinal conductors. Accordingly, each bio-electrical signal is amplified in substantially the same manner.
The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the preferred embodiment(s), taken in conjunction with the accompanying drawings.